The present invention relates to a combination of perfluorocarbon liquid and silicone for treating disorders of an eye and more particularly to a combination of perfluorophenanthrene and silicone as an interoperative tool and methods of treating disorders of an eye with the combination.
Retinal detachment consists of physical separation of the retina from its juxtaposition to the choroid. One of the most important factors contributing to retinal detachment is liquefaction and shrinkage of the vitreous, commonly referred to as vitreous retraction. Additionally, vitreous retraction caused by vitreous shrinkage may produce retinal tear with or without retinal detachment. For more than three decades lighter-than-water vitreous substitutes, such as silicone and gas, have played an important role in management of complicated retinal detachments, providing short and long term tamponading effect on the retina. Although these substances exert some degree of pressure to the upper part of the retina, the loss of support in the inferior part of the vitreous cavity causes accumulation of fluid with subsequent membrane formation in this area. Thus inferior tractional retinal detachments are often seen with the use of low specific gravity silicone oil. Although high specific gravity fluorosilicone was injected inside the vitreous cavity as early as 1962 by Cibis and others, its effect as a tamponading agent and intraoperative tool was not recognized until years later. The impurities present in fluorosilicone have made it less desirable as a high specific gravity vitreous substitute.
In 1966, Clark, one of the co-inventors herein, reported on the use of fluorocarbon liquids as an oxygen transporter and blood substitute. It has been demonstrated that mice immersed for one hour in a liquid perfluorocarbon equilibrated with oxygen at atmospheric pressure could survive by breathing this oxygenated liquid. In 1982, Haidt et al reported the use of liquid perfluorocarbon as a vitreous substitute. Since then numerous experimental studies have demonstrated poor long term tolerance if these substances are injected in the vitreous cavity. Chang was the first to demonstrate the use of perfluorochemicals as an intraoperative tool in the human eye and recommended their removal immediately during the same procedure.
The common characteristics of perfluorocarbon liquids are their higher specific gravity than that of water, which assists in unfolding the retina, specifically in giant retinal tears. Their low viscosity permits injection through small bore needles, as thin as 20 to 30 gauge, simplifying intravitreal injection and subsequent removal. Their surface tension and immiscibility with water enhances their effect on unfolding the detached retina. Table I demonstrates the majority of presently used perfluorocarbon liquids in ophthalmology and their characteristics.
TABLE I ______________________________________ Perfluorocarbon Liquids ______________________________________ Perfluo- Chemical Specific Viscosity rocarbon Formula Gravity (cs, 25 C) ______________________________________ Perfluoro- C.sub.12 F.sub.27 N 1.89 2.6 tributy- lamine Perfluoro- C.sub.8 F.sub.18 1.76 0.8 octane Perfluoro- C.sub.10 F.sub.18 1.94 2.7 decalin Vitreon C.sub.14 F.sub.24 2.03 8.03 (Perfluor- orophenan- threne ______________________________________ Refrac- Surface Perfluo- tive Tension rocarbon Index dyne/cm ______________________________________ Perfluor- 1.29 16 tribyty- lamine Perfluoro- 1.27 14 octane Perfluoro- 1.31 16 decalin Vitreon 1.33 16 (Perfluor- ophenan- threne) ______________________________________
A recurring problem in retinal detachment surgery, especially after the formation of vitreous traction, is maintaining the retina in position until chorioretinal adhesions can form. At present various kinds of gases including air, sulfurhexafluoride, and perfluorocarbons are used to hold the retina in place. However, both giant retinal tears and inferior breaks are difficult to treat with gas.
Experimental studies have demonstrated a new perfluorocarbon liquid (perfluorophenanthrene C.sub.12 F.sub.24, also known as Vitreon which is a registered trademark, to have no toxic effect on the tissue culture grown in cells and to be tolerated in vitrectomized rabbit eyes and primate eyes when left for six weeks in the vitreous cavity. However, perfluorophenanthrene, if left in the vitreous cavity too long, fragments into small globules in the vitreous cavity. This phenomenon, referred to as emulsification, has been attributed to the change in the surface tension of substances in the vitreous which are absorbed into the surface of the globule of perfluorophenanthrene. It would be desirable if the lifetime of perfluorocarbon liquids present in the vitreous cavity could be extended up to 2-3 months for use in complex cases of vitreoretinal detachment requiring a long-term tamponading effect. Therefore, there is a need for a vitreous substitute which does not form small globules in the vitreous cavity.